<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .a {
            width: 300px;
            height: 300px;
            background-color: #f00;
            margin: 100px;
        }
    </style>

    <script>

        // e.offsetX / e.offsetY  距离目标源的坐标






        // 等待页面资源加载完毕
        window.onload = function () {
            

            var oDiv = document.querySelector('.a');
            oDiv.onclick = function (e) {
                var e = e || event;
                console.log(e.offsetX);
            }

        }
    </script>
</head>

<body>

    <div class="a"></div>



</body>

</html>